The present invention relates to a safety switching apparatus and a method of manufacturing the same. The invention particularly relates to a safety switching apparatus having a first and a second input switch, whose respective switch settings define an input-sided manipulated variable redundantly with respect to one another, further having at least one output switching element which is arranged in an output circuit of the safety switching apparatus, and having an evaluation and control unit which drives or controls the at least one output switching element as a function of the defined manipulated variable, wherein the switching contacts of the first and of the second input switch are coupled to one another, in terms of their switch positions, via a common actuating member.
A safety switching apparatus of this type is distributed by the applicant of the present invention under the type designation PNOZ XV2.
The safety switching apparatuses in the meaning of the present invention comprise both autonomous safety switching devices and complex safety controllers and control systems, for example based on a fail-safe PLC controller. Apparatuses such as these are used primarily in the industrial field, in order to carry out switching processes safely. In this context, xe2x80x9csafexe2x80x9d means that the apparatus complies with at least Category 3 of European Standard EN 954-1. By way of example, apparatuses such as these are used in order to stop, or in some other way to change to a safe state, a machine system from which a hazard has originated, as a reaction to the operation of an emergency-off button or the opening of a protective guard door. Since failure of the apparatus in a situation such as this results in a direct hazard to people or else to material values, the fail-safety of safety switching apparatuses is subject to very stringent requirements. This leads to a high level of complexity associated with high costs for the development and manufacture of safety switching apparatuses.
In the known safety switching apparatus, the input-side manipulated variable is a time constant, which governs a delay time for switching off. A delay time such as this is required, for example, in order to make it possible to move moving drives in a controlled manner to a safe rest position when switching off a machine system. In the case of the known safety switching apparatus, the time constant is set by means of two mutually redundant rotary switches, which are arranged one above the other or one behind the other on a common shaft. This configuration is explained in more detail further below, with reference to FIG. 2.
In general, however, the manipulated variable that is to be set may be any input parameter which is relevant for a safety switching apparatus.
The known safety switching apparatus satisfies the safety requirements of Standard EN 954-1 in particular because the two input switches each define the desired time constant separately from one another. The resultant redundancy means that a fault in one of the switches can be identified reliably by the evaluation and control unit. However, this has the disadvantage that a large amount of mechanical complexity is required in the manufacture of the known safety switching apparatus, and this is associated with correspondingly high costs. Furthermore, the configuration of the known safety switching apparatus occupies a comparatively large amount of space, which prevents miniaturization of apparatuses of this generic type, or at least makes it more difficult.
It is one object of the present invention to specify a safety switching apparatus of the type mentioned initially, which is configured in more simple and more space-saving manner while still satisfying the same stringent safety requirements.
According to one aspect of the invention, this object is achieved in that the switching contacts of the first and of the second input switches are spatially arranged in one plane.
In contrast to this, the switching contacts of the two input switches in the known safety switching apparatus are located in two planes which are offset parallel to one another. This means that the two input switches must be mounted in the enclosure of the safety switching apparatus in two separate process steps. In contrast to this, the two input switches in the safety switching apparatus according to the invention can be mounted in a single process step. This simplifies the manufacture, and the safety switching apparatus according to the invention can be produced more cost-effectively.
Furthermore, as will be shown in the following text on the basis of preferred refinements of the invention, the physical space required for the two input switches can be reduced considerably, so that the safety switching apparatus according to the invention can be implemented in a spatially smaller way overall. Nevertheless, despite all this, it is still possible to use input switches which are separate from one another, and are thus redundant with respect to one another. The required fail-safety thus remains completely preserved.
In a preferred refinement of the invention, the actuating member comprises a common mounting element, on which the switching contacts of the first and of the second input switch are arranged such that they are spatially offset with respect to one another.
This measure has the advantage that the switching contacts of the two input switches are constructionally coupled in a very simple, and hence cost-effective, manner. It is thus possible to dispense with couplings, drives and other measures for transmitting a switching movement from the first input switch to the second, without this resulting in any risk of a different operator setting.
In a further refinement of the measure mentioned above, the common mounting element can be rotated for adjustment.
As an alternative to this, it is also feasible to design the common mounting element such that it can be translated for adjustment. In contrast to this, the preferred refinement is particularly advantageous when the two input switches are multiposition switches, since the switching contacts in this case can thus be arranged in a more space-saving manner with respect to one another, and thus in a spatially smaller manner.
In a further refinement of the measures mentioned above, the common mounting element is a mounting disk, on which the switching contacts of the first and of the second input switch are arranged radially offset with respect to one another.
This measure allows the two input switches, which are separate from one another, to be integrated in a particularly spatially small and space-saving manner in a common mechanical structure. Furthermore, this also simplifies the process of installing the input switches in the enclosure of the safety switching apparatus according to the invention.
In a further refinement of the invention, the first and the second input switch as well as the common actuating member are enclosed by a common switch enclosure.
This measure has the advantage that the input switches, which are separate from one another, form a common, intrinsically redundant component, which can be mounted in a very simple and hence cost-effective manner in the safety switching apparatus according to the invention. Furthermore, the fail-safety is improved even further, since the risk of damage to the redundant switch arrangement during the installation process or during any subsequent intervention in the safety switching apparatus is reduced. Furthermore, the safety-relevant switch arrangement is in this way protected particularly well against external environmental influences, such as dirt. This also contributes to improving the fail-safety.
In a further refinement of the invention, the switching contacts of the first and of the second input switch are sliding contacts, which can be moved over stationary contact surfaces by means of the actuating member.
This measure allows a particularly simple mechanical configuration, especially when the switching contacts are arranged on a common mounting element as the actuating member.
In a further refinement of the measure mentioned above, the contact surfaces are conductive track structures which are applied to a printed circuit board.
This measure allows the two input switches to be produced even in very large quantities in a fail-safe manner, thus minimizing the costs for the two input switches. At the same time, it is in this case possible, by means of a suitable design of the conductive track structures, to provide switching paths which include internal circuit logic. As a consequence of this, even complicated circuit schemes can be implemented in a simple and reproducible manner. Furthermore, this measure further improves the fail-safety, since conductive track structures are not subject to any wear, or at most are subject to extremely low wear, during operation of the apparatus, thus largely precluding any faults occurring only subsequently during operation of the apparatus. The risk of subsequently occurring cross-connections or short-circuits is likewise reduced.
In a further refinement of the invention, the first and the second input switches are each multiposition switches.
This measure can be implemented particularly easily in conjunction with the refinements of the invention mentioned above. This has the advantage that the safety switching apparatus according to the invention has a large number of setting options, thus improving its range of use and its adaptability. This means that larger quantities can be produced, and this leads to a cost reduction.
In a further refinement of the invention, the first and the second input switch have input-sided and output-sided connecting contacts or terminal contacts, which are arranged in a matrix structure with respect to one another.
This measure has the advantage that the number of connecting contacts required for the two input switches can be reduced, which likewise allows the physical space required to be reduced. Furthermore, this also simplifies the manufacture process.
In a further refinement of the measure mentioned above, the input-side connecting contacts of the first and of the second input switch are connected to one another.
This measure once again reduces the number of connections required for the two input switches. For example, this measure makes it possible to provide 16 mutually redundant switch positions, that is to say a total of 32 switch positions, with a total of only 12 connecting contacts. As a consequence of this, the physical space for the arrangement according to the invention can be further reduced, and the manufacture process simplified.
In a further refinement of the invention, the evaluation and control unit has two channels, with a first channel being connected to the first input switch, and a second channel being connected to the second input switch.
This measure has the advantage that the safety switching apparatus has a generally redundant design, thus making it possible to achieve a particularly high level of fail-safety.
It goes without saying that the features which have been mentioned above as well as those which are still to be explained in the following text can be used not only in the respectively stated combination but also in other combinations or on their own, without departing from the scope of the present invention.